A great deal of experimental and clinical evidence has suggested that dietary sodium intake may be related to the development and severity of certain forms of hypertension. One possible, but as yet unconfirmed, reason for sodium's toxicity is that it may alter the autonomic nervous system's control of the heart and vasculature. Therefore, the principal objective of the present investigation will be to determine if changes in dietary sodium intake are indeed capable of modifying the nervous system's regulation of the cardiovascular system in conscious rats. The specific aims will be: (1) to determine the effects of various levels of dietary sodium on the basal autonomic control of heart rate and blood pressure and (2) to assess the effects of dietary sodium on the reflex autonomic control of heart rate and blood pressure. Conscious animals and direct methods of blood pressure measurement will be used in the majority of experiments, thus allowing cardiovascular alterations to be studied without interference of anesthetic agents. In addition, parallel experiments will be conducted in anesthetized rats and in vitro to assess the effects of dietary sodium on autonomic function in greater detail. All findings will be related to the long term objective of the study which is to better understand the relationship between sodium and the nervous system in the development of hypertension. One model of experimental hypertension will be studied, desoxycorticosterone-sodium induced hypertension, a model selected upon its direct relationship to dietary sodium intake and evidence suggesting that a neurogenic component is involved in its genesis.